Silyl- and Germyl-Substituted Boranes: Synthesis and Investigation as Potential Atomic Layer Deposition Precursors.

Boranes featuring bulky hypersilyl or supersilyl groups and/or sterically unencumbered trimethylgermyl substituents were synthesized for investigation as potential precursors for atomic layer deposition (ALD) of elemental boron. The envisaged ALD process would employ a boron trihalide coreactant, exploiting the formation of strong silicon-halogen and germanium-halogen bonds as a driving force. The alkali metal silyl and germyl compounds hypersilyl lithium, {(MeSi)Si}Li(THF) (), supersilyl sodium, (BuSi)Na(THF) (, = 2-3), and trimethylgermyl lithium, {MeGeLi(THF)} (), were used for the synthesis of the silyl- and germyl-substituted boranes in this work.

An unusual ionic cocrystal of ponatinib hydrochloride: characterization by single-crystal X-ray diffraction and ultra-high field NMR spectroscopy.

This study describes the discovery of a unique ionic cocrystal of the active pharmaceutical ingredient (API) ponatinib hydrochloride (), and characterization using single-crystal X-ray diffraction (SCXRD) and solid-state NMR (SSNMR) spectroscopy. is a multicomponent crystal that features an unusual stoichiometry, with an asymmetric unit containing both monocations and dications of the ponatinib molecule, three water molecules, and three chloride ions. Structural features include (i) a charged imidazopyridazine moiety that forms a hydrogen bond between the ponatinib monocations and dications and (ii) a chloride ion that does not feature hydrogen bonds involving any organic moiety, instead being situated in a "square" arrangement with three water molecules.

A comparison of the coordination behaviour of RPCHBMe (R = Me Ph) ambiphilic ligands with late transition metals.

A new synthesis that avoids the use of MePH is reported for (MePCHBMe), and this method was extended to the synthesis of (PhPCHBMe). The ligand precursor (MePCHBMe) did not react with [{M(μ-Cl)(cod)}] (cod = 1,5-cyclooctadiene; M = Ir and Rh) or [PtCl(cod)] at room temperature. However, after 12-48 hours at 65-70 °C, these reactions afforded (a) [Ir(cod)(μ-Cl)(MePCHBMe)] (1), (b) an equilibrium mixture of (MePCHBMe), [{Rh(μ-Cl)(cod)}] and [Rh(cod)(μ-Cl)(MePCHBMe)] (2), and (c) -[Pt(μ-Cl)(MePCHBMe)] (3), respectively.

Reactions of [(dmpe)MnH(CH)] with hydrogermanes to form germylene, germyl, hydrogermane, and germanide complexes.

Reactions of the ethylene hydride complex -[(dmpe)MnH(CH)] (1) with secondary hydrogermanes HGeR at 55-60 °C afforded the base-free terminal germylene hydride complexes -[(dmpe)MnH(GeR)] (R = Ph; 2a, R = Et; 2b). Room temperature reactions of 2a or 2b with an excess of the primary hydrogermanes HGeR' (R' = Ph or Bu) afforded -[(dmpe)MnH(GeHR')] (R' = Ph; 3a, R' = Bu; 3b) in rapid equilibrium with small amounts of 2a/b, as well as the digermyl hydride complex -[(dmpe)MnH(GeHR')] {R' = Ph (4a) or Bu (4b)} and the -hydrogermane germyl complex -[(dmpe)Mn(GeHR')(HGeHR')] {R' = Ph (5a) or Bu (5b)}. Pure 3b was isolated from the reaction of 2b with HGeBu, whereas 3a decomposed readily in solution in the absence of free HGePh, and a pure bulk sample was not obtained.

An Unusual Macrocyclic Hexamer of an Iso-Tellurazole N-Oxide Featuring CTe O Chalcogen Bonds is Formed by κ -O Complexation to Fe(II) and Ni(II).

Studies of the supramolecular chemistry of iso-tellurazole N-oxides have been confined to non-polar media until now. To overcome that limitation, an iso-tellurazole N-oxide was derivatized with a primary alcohol group; the compound is soluble in polar solvents and stable in acidic to neutral aqueous media. Nickel (II) and iron (II) form macrocyclic complexes with six molecules of that iso-tellurazole N-oxide in a hitherto not-observed macrocyclic arrangement defined by CTe⋅⋅⋅O chalcogen bonds and κ -O bound to the metal ion.

Uranium(iv) alkyl cations: synthesis, structures, comparison with thorium(iv) analogues, and the influence of arene-coordination on thermal stability and ethylene polymerization activity.

Reaction of [(XA)U(CHSiMe)] (1; XA = 4,5-bis(2,6-diisopropylanilido)-2,7-di--butyl-9,9-dimethylxanthene) with 1 equivalent of [PhC][B(CF)] in arene solvents afforded the arene-coordinated uranium alkyl cations, [(XA)U(CHSiMe)(η -arene)][B(CF)] {arene = benzene (2), toluene (3), bromobenzene (4) and fluorobenzene (5)}. Compounds 2, 3, and 5 were crystallographically characterized, and in all cases the arene is π-coordinated. Solution NMR studies of 2-5 suggest that the binding preferences of the [(XA)U(CHSiMe)] cation follow the order: toluene ≈ benzene > bromobenzene > fluorobenzene.

Coordination chemistry and structural rearrangements of the MePCHAlMe ambiphilic ligand.

Reaction of 2 equivalents of (MePCHAlMe) with [{RhCl(cod)}] (cod = 1,5-cyclooctadiene) afforded [{κ,-(MeAl)ClMeAl(CHPMe)}Rh(cod)] (1), which features a κ-coordinated bis(phosphino)aluminate anion. In compound 1, an Al-Cl substituent bridges to a molecule of AlMe, which could be removed to provide [{κ,-ClMeAl(CHPMe)}Rh(cod)] (2). By contrast, reaction of 1 equiv.

Three-Dimensional Structure and Optimization of the Metallo-β-Lactamase Inhibitor Aspergillomarasmine A.

The aminopolycarboxylic acid aspergillomarasmine A (AMA) is a natural Zn metallophore and inhibitor of metallo-β-lactamases (MBLs) which reverses β-lactam resistance. The first crystal structure of an AMA coordination complex is reported and reveals a pentadentate ligand with distorted octahedral geometry. We report the solid-phase synthesis of 23 novel analogs of AMA involving structural diversification of each subunit (l-Asp, l-APA1, and l-APA2).

Iso-Tellurazolium-Phenoxides: A Family of Te···O Chalcogen-Bonding Supramolecular Building Blocks.

Formal substitution of the oxygen atom of an iso-tellurazole -oxide with deprotonated (, , and )-hydroxyphenyl groups generated molecules that readily aggregate through Te···O chalcogen bonding (ChB) interactions. The molecules undergo autoassociation in solution, as shown by variable temperature (VT) H NMR experiments and paralleling the behavior of iso-tellurazole -oxides. Judicious adjustment of crystallization conditions enabled the isolation of either polymeric or macrocyclic aggregates.

Competing Effects of Chlorination on the Strength of Te⋅⋅⋅O Chalcogen Bonds Select the Structure of Mixed Supramolecular Macrocyclic Aggregates of Iso-Tellurazole N-Oxides.

Chlorination of 3-methyl-5-phenyl-1,2-tellurazole-2-oxide yielded the λ Te dichloro derivative. Its crystal structure demonstrates that the heterocycle retains its ability to autoassociate by chalcogen bonding (ChB) forming macrocyclic tetramers. The corresponding Te⋅⋅⋅O ChB distances are 2.

Reactions of [(dmpe)MnH(CH)]: synthesis and characterization of manganese(i) borohydride and hydride complexes.

Reactions of trans-[(dmpe)MnH(CH)] (1) with BH(NMe), 9-BBN, and HBMes yielded the manganese(i) borohydride complexes [(dmpe)Mn(μ-H)BR] (3: R = H, 4: R = CH, 5: R = Mes). The reaction of 1 with BH(NMe) proceeds via ethylene substitution. By contrast, a detuerium labelling study indicates that the reaction of 1 with HBMes involves initial isomerization of 1 to an unobserved 5-coordinate ethyl intermediate, [(dmpe)MnEt], which reacts with the hydroborane to afford EtBR and [(dmpe)MnH], followed by reaction with a second equivalent of hydroborane to generate 5 (an analogous pathway is likely followed for other base-free hydroboranes such as 9-BBN).

Shedding Light on the Diverse Reactivity of NacNacAl with N-Heterocycles.

The aluminum(I) compound NacNacAl (NacNac=[ArNC(Me)CHC(Me)NAr] , Ar=2,6-iPr C H , 1) shows diverse and substrate-controlled reactivity in reactions with N-heterocycles. 4-Dimethylaminopyridine (DMAP), a basic substrate in which the 4-position is blocked, induces rearrangement of NacNacAl by shifting a hydrogen atom from the methyl group of the NacNac backbone to the aluminum center. In contrast, C-H activation of the methyl group of 4-picoline takes place to produce a species with a reactive terminal methylene.

Reversing Organic-Inorganic Hybrid Perovskite Degradation in Water via pH and Hydrogen Bonds.

The moisture instability of organic-inorganic hybrid perovskite solar cells has been a major obstacle to the commercialization, calling for mechanistic understanding of the degradation process, which has been under debate. Here we present a surprising discovery that the degradation is actually reversible, via in situ observation of X-ray diffraction, supported by FTIR and SEM. To isolate the hydrogen bond effect, water was replaced by methanol during the in situ experiment, revealing the decomposition to be initiated by the breakdown of N-H-I hydrogen bonds.

Adduct of NacNacAl with Benzophenone and Its Coupling Chemistry.

Reaction of NacNacAl (NacNac=[DippNC(Me)CHC(Me)NDipp] ) with one equivalent of benzophenone affords a ketylate species NacNacAl(η (C,O)-OCPh ) that undergoes easy cyclization reactions with unsaturated substrates. The scope of substrates included benzophenone, aldimine (PhNC(Ph)H), quinoline, phenyl nitrile, trimethylsilyl azide, and a saturated cyclic thiourea. The latter substrate reacted by an unusual C-N cleavage that left the C=S functionality intact.

Synthetic and structural investigations of bis(N-alkyl-benzoselenadiazolium) cations.

The synthesis, and spectroscopic and structural characterization of bridged dicationic derivatives of benzo-2,1,3-selenadiazoles are reported. The chloride salt of [HCNSeN-CH-CH-NSeNCH] crystallizes forming a macrocyclic structure in which two cations are bridged by SeCl chalcogen bonds (ChBs), with a third chloride at the centre of the macrocycle. The structure of [1,2-(HCNSeN)-CH]Cl consists of two selenadiazolium cations linked by a chiral cyclohexane and capped by SeCl ChBs.

Interaction of Multiple Bonds with NacNacGa: Oxidative Cleavage vs Coupling and Cyclization.

The reactivity of the gallium(I) compound NacNacGa (4) to a variety of unsaturated compounds has been studied. Whereas 4 proved surprisingly unreactive toward olefins, ketones, guanidines, and thioureas, it reacts with isocyanates and carbodiimides to furnish the products of coupling of two heterocumulenes. With isothiocyanate, the C═S cleavage occurs, leading to the dimer (NacNacGa)(μ-S)(μ-CNPh) and the cyclization product NacNacGa(SC═NPh).

Macrocyclic complexes of Pt(ii) and Rh(iii) with iso-tellurazole N-oxides.

Pt(ii) and Rh(iii) readily form complexes with 3-methyl-5-aryl-1,2-tellurazole 2-oxides (L = (3-Me-5-Ar-1,2-C3HTe(NO)). The aryl group is either phenyl or 3,5-di-tert-butylphenyl, the latter case being a new derivative with enhanced solubility. The compound [Pt(3-Me-5-(3,5-tBu2C6H3)-1,2-C3HTe(NO))4](BF4)2 crystallizes in the P21/C space group featuring a square planar complex in the lattice.

Pyrrolidinium lead iodide from crystallography: a new perovskite with low bandgap and good water resistance.

The crystal structure of a new perovskite material, (C4H8NH2)PbI3 was determined and illustrated by single crystal X-ray diffraction. UV spectra, photoluminescence and XRD results show it is a promising alternative to hybrid organic-inorganic perovskites due to it's good water resistance and suitable bandgap.

Asymmetric Entry into 10-aza-Analogues of Alkaloids Reveals a Pronounced Electronic Effect on Antiviral Activity.

Development of a chiral pool-based synthesis of 10-aza-analogues of biologically active alkaloids is described, involving a concise reductive amination and condensation sequence, leading to ring-B/C-modified, fully functionalized ring-C derivatives. Differentiated anticancer and antiviral activities of these analogues are presented. Despite complete conformational and functional group overlap, the 10-aza-analogues have diminished anticancer activity and no antiviral activity.

Building new discrete supramolecular assemblies through the interaction of iso-tellurazole N-oxides with Lewis acids and bases.

The supramolecular macrocycles spontaneously assembled by iso-tellurazole N-oxides are stable towards Lewis bases as strong as N-heterocyclic carbenes (NHC) but readily react with Lewis acids such as BR (R = Ph, F). The electron acceptor ability of the tellurium atom is greatly enhanced in the resulting O-bonded adducts, which consequently enables binding to a variety of Lewis bases that includes acetonitrile, 4-dimethylaminopyridine, 4,4'-bipyridine, triphenyl phosphine, a N-heterocyclic carbene and a second molecule of iso-tellurazole N-oxide.

Synthesis and structural characterisation of the aggregates of benzo-1,2-chalcogenazole 2-oxides.

Iodine oxidation of bis[2-(hydroxyiminomethyl)phenyl] dichalcogenides yields benzo-1,2-chalcogenazole 2-oxides. Annulated derivatives of iso-tellurazole N-oxides spontaneously aggregate into cyclic tetra- and hexamers through TeO chalcogen bonding; the structures of the co-crystals with benzene and CHCl illustrate the ability of these macrocycles to interact with small guest molecules. The selenium congener crystallizes forming a supramolecular polymer.

Manganese Silylene Hydride Complexes: Synthesis and Reactivity with Ethylene to Afford Silene Hydride Complexes.

Reaction of the ethylene hydride complex trans-[(dmpe) MnH(C H )] (1) with Et SiH at 20 °C afforded the silylene hydride [(dmpe) MnH(=SiEt )] (2 a) as the trans-isomer. By contrast, reaction of 1 with Ph SiH at 60 °C afforded [(dmpe) MnH(=SiPh )] (2 b) as a mixture of the cis (major) and trans (minor) isomers, featuring a Mn-H-Si interaction in the former. The reaction to form 2 b also yielded [(dmpe) MnH (SiHPh )] (3 b); [(dmpe) MnH (SiHR )] (R=Et (3 a) and Ph (3 b)) were accessed cleanly by reaction of 2 a and 2 b with H , and the analogous reactions with D afforded [(dmpe) MnD (SiHR )] exclusively.

A Synthetic, X-ray, NMR Spectroscopy and DFT Study of β-Naphthil Dihydrazone, Di(β-naphthyl)acetylene, Tetra(β-naphthyl)cyclopentadienone, and Hexa(β-naphthyl)-benzene: C (C H ) Is a Disordered Molecular Propeller.

Treatment of β-naphthil dihydrazone, 1, with silver oxide yields di(β-naphthyl)acetylene, 2, which undergoes Diels-Alder cycloaddition with tetra(β-naphthyl)cyclopentadienone, 4, to give hexa(β-naphthyl)benzene, 5, upon decarbonylation. Molecules 1, 2 and 4 have been characterised by X-ray crystallography, but hexa(β-naphthyl)benzene exhibits rotational disorder of the peripheral substituents. Nevertheless, calculations at the density functional level reveal the favoured structure of 5 to be a molecular propeller, in which the eight possible rotamers are essentially iso-energetic.

Zinc Chelation by a Small-Molecule Adjuvant Potentiates Meropenem Activity in Vivo against NDM-1-Producing Klebsiella pneumoniae.

The widespread emergence of antibiotic drug resistance has resulted in a worldwide healthcare crisis. In particular, the extensive use of β-lactams, a highly effective class of antibiotics, has been a driver for pervasive β-lactam resistance. Among the most important resistance determinants are the metallo-β-lactamases (MBL), which are zinc-requiring enzymes that inactivate nearly all classes of β-lactams, including the last-resort carbapenem antibiotics.

Supramolecular macrocycles reversibly assembled by Te(…)O chalcogen bonding.

Organic molecules with heavy main-group elements frequently form supramolecular links to electron-rich centres. One particular case of such interactions is halogen bonding. Most studies of this phenomenon have been concerned with either dimers or infinitely extended structures (polymers and lattices) but well-defined cyclic structures remain elusive.